How they see
How does a bat see the world?
Not blind — many bats see ultraviolet
'Blind as a bat' is simply wrong: most bats see perfectly well, and many can even detect ultraviolet light. What they lack is fine detail. Their visual picture stays coarse because, for the precise business of catching insects in the dark, they lean on echolocation instead. Vision handles the bigger picture; sound handles the sniper work.
See through their eyes
Human ≈ 60 cpd (20/10)
How sharp is a bat's vision?
Its eyes resolve about 1.5 cycles per degree (20/400 (est.)), while a human reaches around 60 cpd (20/10). Its field of view spans about 180°.
How does a bat see a human?
Its eyes resolve about 1.5 cycles per degree against your 60, so a face has to be roughly 40 times closer for it to pick out the detail you do. Your outline and your movement read clearly; your expression does not.
Colour comparison
How each colour shifts when seen through this animal's eyes, using the same colour model as the app. Tones a screen can't emit (such as ultraviolet) are shown as an approximation.
What colours can a bat see?
Dim, coarse colour with ultraviolet sensitivity in many species.
Photoreceptors
Rod-dominated retina with S (often UV) and L cones
Cone peak sensitivities
- S (UV/violet)365 nm
- L (green)550 nm
How does a bat see in the dark?
Excellent — rod-dominated for night flight.
How does a bat's vision compare to a human's?
A bat's detail is coarse, perhaps 20/400 to your 20/20. Its rod-rich eyes are superb in the dark where yours falter, and many bats see ultraviolet light that you cannot.
What is special about a bat's vision?
- Many species see UV
- Echolocation is the primary sense
- Very low acuity
What the research shows
The case against "blind as a bat" was built from several lines of evidence. Müller et al. (2009) examined two leaf-nosed bats, Glossophaga soricina and Carollia perspicillata, and found ultraviolet-sensitive cones among the dominant rods; electroretinograms showed raised UV sensitivity, and the cornea and lens let light near 350 nm reach the retina. Winter, López & von Helversen (2003) added the behavioural proof that a nectar-feeding bat can actually use ultraviolet light. The cone peaks listed on this page are inferred from the type of opsin present rather than measured cell by cell.
Everything spatial is far less secure. Acuity in bats with tiny eyes is estimated at 1–2 cpd, and the simulation uses 1.5 cpd; the field of view varies between species, and flicker fusion has not been measured well enough to state. Findings from two plant-visiting species should also not be stretched to every bat, because cone complements differ across the group. The biggest limit of any screen version is not optical at all: echolocation, which does the precise work of catching insects, builds its picture from sound, and nothing on a display can reproduce it. The ultraviolet channel cannot be displayed either, so a violet highlight can only stand in for it.
Guides: Animals that see ultraviolet · Which animal has the best eyesight? · All guides
Scientific sources
- Müller et al. (2009)
- Winter, López & von Helversen (2003)
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